1. Field of the Invention
This invention relates to an image inverting device, and in particular to an image inverting device having a function to stop the rotation of an image acquired as it moves round, and suitably employed on a rotating imaging device.
2. Description of the Related Art
Monitoring devices using television cameras are in wide use. FIG. 17 shows an installation of such a television camera, wherein, for example, a mounting stand 1 is attached to the underside of a ceiling, and a television camera 2 is installed on the mounting stand 1. A cable 3 is pulled out from the television camera 2.
FIG. 18 shows an example wherein the television camera 2 is fitted to a pole 4. Herein, the television camera 2 is attached to the upper end of the pole 4 on a rotation stand 5, and is covered by a case 6. In this arrangement, the television camera 2 can be rotated through a predetermined angle.
In order to acquire a wide image of the surroundings, the television camera 2 may be rotated through a large rotation angle around the mounting stand 1 or rotation stand 5 on which the television camera 2 is fitted. However as the cable 3 connected to the television camera 2 becomes twisted, there is a limit to the rotation angle and there is therefore a problem in that television camera 2 cannot be rotated through any desired angle in any desired direction.
It may be possible to use a slip ring or the like to avoid using the connecting cable 3 which limits the rotation of the television camera 2. However, in the case of a slip ring, noise tends to arise from the sliding contact, and there is a problem in that the apparatus cannot be made compact. Another method has been proposed wherein signal transfer is performed using radio communication, but such a method has many disadvantages such as battery life, leaking of information over the radio, decline of image quality due to radio bandwidth limitations, and intermixture of radio noise.
The television camera 2 may also be rotated directly without using the connecting cable, but this has the disadvantage of requiring a large space. That is, when monitoring is performed by the television camera, it is installed so that the axis of the television camera is aligned in an effectively horizontal direction. If it is made to rotate in such a state, a large space is required to rotate the television camera 2, and this is therefore unsuitable for imaging in a confined space.
An object of this invention is to resolve the above problems, to provide an image inverting device wherein, although the image is acquired while the device moves round, the image does not rotate, and to provide a rotating imaging device which can acquire a rotation image with no limitation without rotating the image receiving means itself.
Another object of this invention is to provide a device, wherein rotation of the image is stopped and a non-rotating image can be obtained.
A further object of this invention is to provide a device, wherein 360 degree rotation imaging can be performed without rotating the image receiving means, and the image does not rotate in this process.
According to one aspect of this invention, there is provided an image inverting device comprising:
an objective mirror which reflects an image light, incident on a rotation axis from the side of the rotation axis, in the direction of the rotation axis,
an inverting unit on which the image light reflected by the objective mirror is incident, which reflects the image light such that the light rotates around the rotation axis due to the rotation of this unit, and which emits the image light in the direction of the rotation axis, and
rotation drive means for rotating the objective mirror and the inverting unit respectively so that a predetermined relation exists between them.
The objective mirror and inverting unit may be respectively rotated in the same direction around the rotation axis such that the ratio of their angular velocities is 2:1. The inverting unit may comprise an assembly of an odd number of reflecting mirrors. The inverting unit may also comprise an optical block comprising an odd number of reflecting surfaces. The inverting unit may also comprise a Dove prism.
Another invention relates to a image inverting device comprising:
an image inverting device, and
an image receiving means disposed so that its optical axis coincides with the rotation axis of the inverting device for receiving the image light emitted by the inverting unit.
The image receiving means may be a television camera or a video camera. The image receiving means may comprise a focussing lens which focuses the image light emerging from the inverting unit to an image, and a linear image receiving means which is disposed at the focal point of the focussing lens and extends in a perpendicular direction to the direction in which the image moves when the objective mirror rotates. Also, reading from the linear image receiving means may take place in synchronism with the rotation of the objective mirror.